The present invention relates to a developing device, a process cartridge including the developing device, and an image forming device including the developing device.
Normally, conventional image forming devices include a toner holding chamber or a toner container where toners are contained therein and a developing chamber where a developing roller is provided. An opening is formed at a boundary between the toner holding chamber and the developing chamber, so that the toners are transferred through the opening into the developing chamber. The conventional image forming devices are configured to detect the remaining amount or toner in a developing unit, and once the remaining amount has reached a predetermined value of less, urge the user to replenish the toner. There are many different ways to detect the amount of remaining toner. In one exemplary method, light transmission windows are provided in the toner holding chamber of a developing unit. A light emitting element and a light receiving element are provided, one in confrontation with each of the light transmission windows. The amount of remaining toner in the toner holding chamber is detected by emitting light from the light emitting element so that the light passes through both the light transmission windows. The amount of remaining toner will correspond to the amount of light received by the light receiving element.
However, with this method, it becomes impossible to accurately detect the amount of remaining toner when toner clings to the light transmission windows. Therefore, a cleaning member for cleaning the light transmission window is provided in the toner holding chamber. The cleaning member is configured to slide across and clean the light transmission window while rotating integrally with a toner agitation/transfer member. The toner agitation/transfer member is provided in the toner holding chamber, in order to agitate and transport the toner in the toner holding chamber.
The devices disclosed in Japanese Patent-Application Publication (Kokai) No. HEI-7-56431 or Japanese Patent-Application Publication (Kokai) No. HEI-9-34238 measure the time from when the cleaning member cleans the light transmission window to when the light path is blocked by toner that falls from the toner agitation/transfer member. However, as described in Japanese Patent-Application Publication (Kokai) No. HEI-7-56431, the fluidity of toner changes with changes in environmental conditions and with the length of use. Consequently, the toner falls from the toner agitation/transfer member at various timings, depending on the fluidity of the toner, so that it is impossible to stably detect the remaining amount of toner.
The length of time from when the light transmission windows are wiped until the light transmission windows are covered by toner depends on the amount of toner that drops from the agitator (after the agitator passes by the opening), and on the amount of the toner that billows up into a cloud-like condition in the chamber. However, these amounts will change with changes in the fluidity of the toner. Therefore, the amount of remaining toner can only be detected with extreme instability and inaccuracy.
Also, conventional image forming devices have a problem in that the toner is not always evenly distributed through the toner chamber. For example, when a laser beam printer is transported or when a developing cartridge is taken out and inserted into the laser beam printer for replacement, the toner tends to collect in one end of the toner chamber, so that it is impossible to accurately detect the remaining amount of the remaining toner. Also, when the opening from the toner chamber into the developing chamber is narrower than the developing chamber itself, or when narrow width sheets, such as envelops or postcards, are consecutively printed in large numbers, then toner is consumed unevenly from the toner chamber. The toner will be distributed unevenly in the toner chamber as a result. For this reason, it is difficult to properly detect how much toner remains in the toner chamber.
When a sheet-shaped member is provided to rotate in the toner chamber to agitate the toner, the ends of the sheet-shaped member can slidingly contact against the light transmission windows provided at both end walls of the toner chamber. In such a situation, the sheet shaped member damages the surface of the light transmission windows so that detection of remaining amount of toner cannot be properly performed.
To prevent damage to the light transmission windows, the sheet shape member can be formed shorter than the length of the toner chamber, so that the ends of the sheet shaped member are separated from the walls of the toner chamber. However, with this configuration, toner can accumulate in the space between the side walls of the toner chamber and the ends of the sheet shaped member, so that it is impossible to prevent uneven distribution of toner in certain areas of the toner chamber.
Some image forming device include a screw member to agitate the toner in the toner chamber. The screw member positively transports toner in the toner chamber along the lengthwise direction of the toner chamber. With this configuration, it is difficult to uniformly distribute the toner on both upstream and downstream sides of the transport direction along the screw member. As a result, deviation in the toner accumulation may occur.
In another aspect, when using the developing system that uses non-magnetic single-component toner, the toner must be scraped between a layer thickness regulating member and the developing roller in order to uniformly charge the toner. In conventional devices, the layer thickness regulating blade is usually made from stainless steel and the like in order to reduce production costs. Where the layer thickness regulating blade abuts against the developing roller, the layer thickness regulating blade applies a large pressure onto external additive of the toner. This can force the external additive to become embedded into the base particle of the toner, thereby reducing the fluidity of the toner. When such toner with reduced fluidity is returned from the developing chamber to the toner holding chamber with circulation of toner between toner developing chamber and the toner holding chamber, the time required after the toner with reduced fluidity is agitated by the agitator until the toner settles on the floor of the toner holding chamber may fluctuate depending on how long the toner has been used. This makes it difficult to stably detect the amount of remaining toner. When the amount of the toner with reduced fluidity in the toner holding chamber increases, the toner can become unevenly distributed in the toner holding chamber so that reliable and accurate remaining toner detection cannot be performed.
In still another aspect, the conventional image forming devices need to reliably agitate toner throughout the entire toner holding chamber by provision of a toner agitation/transfer member. The toner agitation/transfer member is disposed to slide against the inner floor surface of the toner holding chamber, with its tip in a bent condition. Also, the toner agitation/transfer member is formed to a width sufficient to substantially contact both walls at lengthwise ends of the toner chamber.
However, when the agitation/transfer member contacts both side surfaces of the toner holding chamber while rotating, the light transmission windows will be scraped off by the agitation/transfer member, in addition to being cleaned off by the cleaning member. Accordingly, the agitation/transfer member removes toner from the light transmission windows at a timing that matches the rotation cycle of the agitation/transfer member, so that light will sometimes, depending on the amount of friction, pass through the light transmission windows at this unwanted timing. Because light passes through the light transmission windows in an unstable manner, improper detection of remaining toner may occur.
Further, in the conventional developing devices, components of the toner can be spread in a thin film onto the light transmission window. This phenomenon is referred to as xe2x80x9cfilmingxe2x80x9d. Filming reduces the precision of remaining toner detection because it obstructs light from passing through the light transmission windows even directly after the cleaning member wipes off the light transmission windows. When insufficient light passes through the light transmission windows, then detection results will appear as though toner fills the toner holding chamber, regardless of whether any toner is actually positioned between the two light transmission windows or not.
Further, sometimes in the conventional developing devices, the light receiving element generates an output signal because a light path is opened between the light generating element and the light receiving element when the agitation/transfer member agitates the toner in the toner holding chamber. Even if the agitation/transfer member is sufficiently separated from the light transmission windows so it does not contact the light transmission windows, the toner near the light transmission windows can be transported with the toner agitated by the agitation/transfer member if the fluidity of the toner has changed because the toner has been used for a long time, or because of environmental conditions such as high temperature and high humidity. Therefore, erroneous output from the light receiving element cannot be completely prevented. For this reason, sometimes the light receiving element receives a light at a timing where it should not normally receive the light. As a result, the remaining amount of toner cannot be stably detected.
It is an object of the present invention to provide an image forming device, or a developing device used in an image forming device, that is capable of stably detecting remaining amount of toner, regardless of the fluidity of the toner.
Another object of the present invention is to provide such image forming device with light transmission windows that are used during detection of remaining amount of toner, and to such developing device used in such an image forming device, wherein toner can be reliably distributed evenly in the toner holding chamber and wherein the remaining amount of toner can always be accurately detected.
Still another object of the present invention is to provide the image forming device, and the developing device used in the image forming device, that is capable of performing stable detection of remaining toner even when non-magnetic single-component toner is used.
Still another object of the present invention is to provide the developing device capable of detecting amount of remaining toner with a high degree of precision, and capable of properly cleaning off the light transmission window while maintaining the toner in the toner holding chamber in a properly agitated condition.
Still another object of the present invention is to reliably prevent filming of the toner on the light transmission window so that the amount of remaining toner can be detected with high precision in the developing device that detects the amount of remaining toner using light transmission windows.
These and other objects of the present invention will be attained by providing a developing device including an improved combination of a developing housing, a developing agent container, a light transmission window, a cleaning member, and a developing agent agitating and transferring member. The developing agent container is connected to and positioned beside the developing housing and is formed with an opening in communication with the developing housing. The developing agent container has a container wall and an inner surface defining an developing agent accumulation space. The light transmission window is provided at the container wall to permit a detection light to pass through the light transmission window so as to detect an amount of the developing agent in the developing agent container. The cleaning member is disposed in the developing agent container and is rotatable at a constant angular velocity about a rotation axis in a direction to move upward when passing beside the opening. The cleaning member is movable to a cleaning position in sliding contact with the light transmission window for cleaning the light transmission window. The developing agent accumulation space is divided into an imaginary first region and an imaginary second region by an imaginary vertical plane passing through the rotation axis and extending in an axial direction of the rotation axis. The imaginary first region is in communication with the opening, and the imaginary second region is positioned opposite the opening with respect to the imaginary vertical plane. The developing agent agitating and transferring member is disposed in the developing agent container for agitating the developing agent in the developing agent container and transferring the developing agent to the developing housing. The developing agent agitating and transferring member includes a blade movable with respect to the inner surface of the developing agent container. The blade is rotatable about the rotation axis of the cleaning member at a constant angular velocity equal to the angular velocity of the cleaning member. The blade is spaced away from the cleaning member in such a manner that the blade is positioned in the imaginary second region when the cleaning member is in the cleaning position.
In another aspect of the present invention, there is provided a developing device including the developing housing, the developing agent container, the light transmission window, the cleaning member, and a developing agent agitating and transferring member. The developing agent agitating and transferring member is disposed in the developing agent container for agitating the developing agent in the developing agent container and transferring the developing agent to the developing housing. The developing agent agitating and transferring member includes a blade movable with respect to the inner surface of the developing agent container. The blade is rotatable about the rotation axis of the cleaning member at a constant angular velocity equal to the angular velocity of the cleaning member. The light transmission window is positioned in the imaginary first region, and the blade is spaced away from the cleaning member in such a manner that the blade is positioned higher than the light transmission window when the cleaning member is in the cleaning position.
In still another aspect of the invention, there is provided a developing device including a developing housing, a developing agent container connected to and positioned beside the developing housing and formed with an opening in communication with the developing housing, the developing agent container having a container wall and an inner surface defining an developing agent accumulation space, a light transmission window provided at the container wall to permit a detection light to pass through the light transmission window so as to detect an amount of the developing agent in the developing agent container, a cleaning member disposed in the developing agent container and movable to a cleaning position in sliding contact with the light transmission window for cleaning the light transmission window, and a developing agent agitating and transferring member disposed in the developing agent container for agitating the developing agent in the developing agent container and transferring the developing agent to the developing housing, the developing agent agitating and transferring member comprising a blade movable with respect to the inner surface of the developing agent container, the developing agent container having a width extending in a widthwise direction of an image recording sheet, and the light transmission window having a window plane extending in a direction perpendicular to the widthwise direction, the developing agent agitating and transferring member being positioned spaced away from the light transmission window by a predetermined distance in the widthwise direction.
In still another aspect of the invention, there is provided a developing device including a developing housing, a developing agent carrying member disposed in the developing housing and having a longitudinal length extending in a widthwise direction of an image recording sheet, the developing agent comprising polymerized toners produced by polymerization method, a developing agent container connected to and positioned beside the developing housing and formed with an opening in communication with the developing housing, the developing agent container having a container wall and an inner surface defining an developing agent accumulation space, the opening having a length corresponding to the longitudinal length of the developing agent carrying member, and a light transmission window provided at the container wall to permit a detection light to pass through the light transmission window so as to detect an amount of the developing agent in the developing agent container, the container wall of the developing agent container including confronting side walls at widthwise ends in the widthwise direction, the light transmission window being disposed at each side wall to allow the detection light to pass through the respective light transmission windows.
In still another aspect of the invention, there is provided a developing device including a developing housing, a developing agent carrying member disposed in the developing housing and having a longitudinal length extending in a widthwise direction of an image recording sheet, the developing agent comprising polymerized non magnetic single component toners produced by polymerization method, a developing agent container connected to and positioned beside the developing housing and formed with an opening in communication with the developing housing, the developing agent container having a container wall and an inner surface defining an developing agent accumulation space, the opening having a length corresponding to the longitudinal length of the developing agent carrying member, the developing agent carrying member carrying thereon the developing agent supplied from the developing agent container into the developing housing through the opening, a light transmission window provided at the container wall to permit a detection light to pass through the light transmission window so as to detect an amount of the developing agent in the developing agent container, the container wall of the developing agent container including confronting side walls at widthwise ends in the widthwise direction, the light transmission window being disposed at each side wall to allow the detection light to pass through the respective light transmission windows, and a thickness regulation member disposed in confrontation with the developing agent carrying member to regulate a thickness of a layer of the developing agent formed on the developing agent carrying member, the thickness regulation member having a pressing segment formed of a rubber pressing against the developing agent carrying member.
In still another aspect of the invention, there is provided a developing device including a developing housing, a developing agent container connected to and positioned beside the developing housing and formed with an opening in communication with the developing housing, the developing agent container having a container wall and an inner surface defining an developing agent accumulation space, a light transmission window provided at the container wall to permit a detection light to pass through the light transmission window so as to detect an amount of the developing agent in the developing agent container, and a cleaning member disposed in the developing agent container and movable to a cleaning position in sliding contact with the light transmission window for cleaning the light transmission window, the light transmission window protruding inwardly with respect to the container wall toward a center of the developing agent accumulation space.
In still another aspect of the invention, there is provided a developing device including a developing housing, a developing agent container connected to and positioned beside the developing housing and formed with an opening in communication with the developing housing, the developing agent container having a container wall and an inner surface defining an developing agent accumulation space, the developing toner comprising a non magnetic single component toner, a developing agent carrying member disposed in the developing housing for carrying thereon the developing agent supplied from the developing agent container into the developing housing through the opening, a light transmission window provided at the container wall to permit a detection light to pass through the light transmission window so as to detect an amount of the developing agent in the developing agent container, and a thickness regulation member disposed in confrontation with the developing agent carrying member to regulate a thickness of a layer of the developing agent formed on the developing agent carrying member, the thickness regulation member having a pressing segment formed of a rubber pressing against the developing agent carrying member.
In still another aspect of the invention there is provided a developing device including a developing agent container having a container wall and an inner surface defining an developing agent accumulation space, a light transmission window provided at the container wall to permit a detection light to pass through the light transmission window so as to detect an amount of the developing agent in the developing agent container, a cleaning member rotatably provided in the developing agent container and performing cleaning to the light transmission window at a predetermined cycle, a developing agent agitating and transferring member rotatably provided in the developing agent container for agitating the developing agent in the container and transferring the developing agent, and a shielding member movably disposed in the developing agent container and shielding the light transmission window for a predetermined period in timed relation with the predetermined cycle.
In still another aspect of the invention, there is provided a process cartridge detachably assembled in a cartridge accommodation space of an image recording device, the cartridge including a latent image carrying member, a developing agent carrying member positioned in confrontation with the latent image carrying member, and the developing device as described above, the latent image carrying member and the developing agent carrying member being disposed in the developing housing. The developing agent carrying member is positioned in confrontation with the latent image carrying member.
In the process cartridge, the developing agent container can be detachable from a case of the cartridge. In other words, the developing agent container disposing therein the cleaning member and the developing agent agitating and transferring member and containing therein the developing agent can be one unit which is separate from the developing agent carrying member and the latent image carrying member. When the developing agent container is assembled to the case of the cartridge, the process cartridge results.
In still another aspect of the invention, there is provided an image recording device including means for detecting a residual amount of a developing agent, and the developing device described above. The detecting means detects the residual amount of the developing agent accumulated in the developing agent container and including a light emitting element and a light receiving element positioned in alignment with the light transmission window.